FPS issues in Developers mode

Hi, i run MSFS in developers mode, i noticed now in flight the FPS seems locked at max 30fps, while in menu its 60fps, has anyone else come across this, have i inadvertently altered a DEV setting, defo not V sync both in game and Nvidia, any thoughts appreciated. I was wondering if this was something to do with Xbox.
Regards Dominic.

PC windows, download.